Electrotelescopy



L. SILBERSTEIN ELECTROTELESGOPY Jan. 5, 1932.

Filed Feb. 15, 1929 2 Sheets-Shee ludw l fi zersiziw,

BY W4 ATTORNEY Jan. 5, 1932. 1., SILBERSTEIN 1,839,706

ELECTROTELESCOPY Filed Feb. 15, 1929 2 Sheets-Sheet 2 INVENTOR Zudwfli/ Silbers ifs/i 24 BY A9. W

ATTORNEY Patented Jan; 5, 1932 LUIDWIK SILBERSTEIN, INCOMPETENT, or nocscns rnn,

ROCHESTER,

MAR-KITS, COMMITTEE, OF

insane ss'ra'rss PATENT QFFICE new YORK, BY CHARLES w. new YORK; SAID LUDWIK SILBERSTEIN,

BY DEGREE OF UOUBT NCX IV COMPETEITT, ASSIGNOR, BY MESNE ASSIGNMENTS, T UNITED CORPORATION, OF LONG-ISLAND CITY, NEW YORK ELECTRQTELESCOPY Application filed FebruaryJE. 1929. Serial No. 340,198.

This invention relates to electro-telescopy (the electrical transmission of picturesor images over wire conductors or other channels), commonly known in the art as picture transmission or television.; In the electrical transmission of pictures, as it is commercially practiced, it is necessary to have scanning discs, each providedwith a series of holes spirally spaced aroundits g periphery, one of which discs is located at the receiving end and the other at the transmitting end. These discs are rotated atgreat speed, preferably in the neighborhood or" 1000 R. P. M. by motors at the transmitting 1.5 and receiving ends which mustv operate in close phase synchronization and in addition there must be nofl'nctuation 0-fspeedoi the motor at the transmitting'end. Such equipment ishighly complicated and difiicult to maintain in efiicient operating'condition,'

In accordance with one feature of thepres ent invention it is proposed to; replace the motor-driven scanning discs with their elabe orate synchronizing means, by vibratingrods, one located. at the transmitting end and'the other at the receiving end. The characteristics of these rods are such that'they vibrate in identical paths when oncetheyhavejbeen started in motion. Another feature of the inventionrelates to the use'of a scanning elementwhichl'hasflee vibrations of two different periods in two different directions, the ratios of the periods being expressed by rather large co -prime numbers difi'ering from each other by a small number. I .I V L p, 7 Another feature of the inventionrelates to the use oia scanning element which sweeps the area of the picture or image t be. trans} mitted in a path corresponding to a Lissajous curve. g L An additional feature ofthe invention is a scanning element whichin its operationfollows apath that iSfthG resultant of two simple harmonic motions. A further feature of the invention is the arrangementof the photoelectric cell or other; scanning device so that it moves inprecise contact with the optical imageats allztimes during thetransmission. of the picture.

These and other featuresof the invention will be understood from the description and the claims when taken with the drawings in which Fig. 1 is a diagrammatic view of the invention representing a. transmitting station and a receiving station; Fig. 2 is a diagrammatic showing of a photoelectric cell and a two-stage vacuum tube amplifier suitable for use in the system of Fig. 1; Fig.3 is a view partially in section of a receiving element for use at the receiving station; Fig. 4 is a diagrammatic showing of in which the scanning elements at the transmitting and receiving stations may be synchronized'; Fig. 5 represents a picture or image to be transmitted which has been shown as comprising a plurality of rectangular picture areas with an incomplete Lissajous curve indicated thereon to define in part the path followed by the scanning ele* ments; and F ig. 6 is a simplified diagram whose purpose is only toexplain the manner in which the whole path or Lissajous curve is completed, whereas Fig. 5 shows only part of the path. i v

. When an elastic rod,-of rectangular section, clamped at one end is set in oscillation,

the manner.

it will have different vibration properties in the cur've would be extremely complicated and when'the ratio is irrational such as I I it/ the curve becomes infinitely entangled and the vibrating end willin the course of time comeinfinitely close to every polnt'in the area of its vibrations, that is,it will practically sweep the entire area contained within the amplitude. of the two component vil'orations;

Furthermore, if two such rods are identical and both are set in motion by forces exerted in the same direction at the same instant, they will synchronously pass through corresponding points. If the actuating force on one rod is greater than that on the other, but the direction and point of impact are the same in both cases, one path will be similar to, only of less amplitude than the other. This lurnishes a very accurate, simple and inexpensive means for use in television systems wherein the end of one rod serves to scan the image to be transmitted while the other acts as a reception instrument.

In the transmission of pictures it has een found that efficient results are obtained where the picture or image is considered being made'up of approximately 2500 small areas and then scanning each of these areas. In accordance with the principles t vibrating rods as outlined above it is proposed to have the ratio of the periods T andT of componentoscillations bear the ratio of two large co-prime numbers differing from each other by a small number such as is represented by the ratio 49:50. The picture or image A of Fig. 5 comprises 2&50 rectangles corresponding to the ratio 49 to 50 and laid out for tracing a Lissajous curve passing as a diagonal through each one of these rectangles. This curve L has been traced only in part on this figure since the completeeurve would represent such a complicated pattern that it would be confusing, but the method of tracing such a Lissajous curve is wellknown even to students of elementary physics. However, in Fig. 6 a simple picture comprising rectangles bearing the ratio of 4 to 5, is shown, which explains the matter simply. It will be noted that these diagonals of this curve'cross each rectangle so that if a scanning device follows this pattern, every -rectangular area of the image will be crossed. 1 I

In putting the invention into practical form as shown in Fig. 1, two rods or bars of rectangular cross-section such as 10 and 11 are provided, each mounted with one end rigidly fastened to a support such as'12 and 13. At the transmitting station the free end of the rod 10 is provided with a photoelectric cell 14'. In this showing A represents an image to be transmitted which may be an illuminated transparency such as a positive or an image of an objector person projected by a lens 15 mounted in a camera. For focus ing the image, aground glass 16 may be used but it will be understood that this glass is removed during the transmission of the picture and that the photoelectric cell 14 is in precise contact with the actualoptica-l image of the object A as projected by the lens 15. While the end'of the rod 10 is shownprovided with a light responsive photoelectric cell it will. be understood that a perforated dark screen vibrated very close to the image plane including vacuum tube 21, the output of which is coupled to the second stage of the amplifier including a second vacuumtube 22. It is unnecessary here to explain the operation of this amplifier since it is well'known in the art. It is sulficient to state, however, that the weak photoelectric currents developed by the photoelectric cell 1 1 are successively amplified by the two vacuum tubes 21 and 22 and delivered as amplified current to the con ductors 23 leading to a light valve 24: at the receiving station.

This light valve transmits from a constant light source, placed at the receiving station, light of an intensity proportional, at any in stant, to the intensity of the arriving photoelectric current. It may consist essentially oi a narrow ribbon-like c0ndu'ctor'25 in series with the conductors 23, which conductor lies in a transverse magnetic field in such a position as to entirely cover a small aperture 26. The incoming current passing through the ribbon 25 is consequently deflected to one side by the interaction of the current with the magnetic field thus exposing and permitting light to pass through the aperture 26 at varying intensities. This light valve may be similar in form to that developed by E. C. Wente disclosed in Bell System Technical Journal, Volume IV, April 1925.

It has been mentioned that at the receiving station a vibrating rod 11 identical in characteristics with the rod 10 at the transmitting station, is provided. The rod 11 at its free end carries a mirror shown in dotted lines at 27 so that a source of light 28 and a lens 29 transmit light on the aperture 26 of the light valve so that if the ribbon 25 uncovers this aperture in response to control from the transmitting station varying light corresponding to the image thereat is projected on the'mirror 27 where it is reflected onto a screen 30. Y I l The rod 11 is adjustable into precise synchronism with the rod 10. at the sending station by simply shifting the position of a mobile mass 40 by means of a micrometric screw, along the receiving rod. In order to determine'the exact synchronism of the sending and receiving rods the picture or image may be provided with a fiducial marl: such as X (Fig. 5) in an obscure portion of the field, the weight 40 being adjusted untilthe reproduced mark X is distinctly seen. It will be noted that an electromagnet 31 1s provided at the transmitting station to set in vibration the rod 10 and a similar electromagnet 32 is provided at the receiving end to set in vibration the rod 11. These electromagnets are included in a series circuit which is controlled by a switch 33, and they are placed in the same position relative to their respective rods so that the magnetic fields of force operate along the diagonals of the crossbration of a few hundred to several thousand 4 station coinpri a second is easily obtainable, determined by the length, stiffness and cross-sectional dis mensions of the rods which may be made of material such as high quality steel or invar as is used for tuning forks.

hat is claimed is r 1. In a system for the electrical transmission of pictures, a single rod rigidly supported at one end, said rod having two different periods of vibrations in planes at an angle to each other, means controlled by the free end of said rod for translating varying light from a picture to be transmitted into varying electrical signals corresponding thereto, and means for setting said rod into free vibration to sweep over the entire area of said picture.

2. In a system forthe electrical transmission of pictures, a single rod rigidly supported at one end, a photoelectric device controlled by the movement of the free end of said rod, and means for setting said rod into free vibration in two different directions.

3. In a system for the electrical transmis sion of pictures, a rod rigidly supported at one end, two lateral dimensions of said rod and therefore also the two corresponding periods of vibrations being expressed by two large co-prime numbers differing from each other by a small number, a photoelectric device controlled by the movement of the free end of said rod, and means for setting said rod into free vibration.

4. In a system for the electrical transmission of pictures, a rod supported at one end and carrying a light cell at its free end, said rod having two unequal cross-sectional dimensions, and means for setting said rod into vibration by an impulse applied diagonally to one side thereof. i

In a system for the reception of pictures transmitted electrically, a single rod having two periods of vibrations in directions at an angle to each other rigidly supported at one ot. :1 'clani'pedat, ne; end and car-winger light cell v i djd, itha inirr'oriatits fre'e end, for proje'cti g li ht on said mirror 'cordingtofthefilgtriallyjtnansmittedpica r fleinng "saidroddiagon-v efe drh reof to follow a L" saijousj curve. i lec tricga'l transmission u'res. a r'oidatjthe transmitting station means respon Y1 at'its'fitcefend'said rod having such characterist'csthat its free enarono s a path corresponding to a ousc'urve, inea'ns'inclr 'nga rod a the receivii'igstation for re- 'p du'ci'n lectrically transmitted eel-na t' ansrn tting being rigidly clamped at oneIend. and means "includin a mobile weight-adjustable on said v'ing rod for adjus'ting it into exact syn 'ei ronism w th fir r0 1- on of pi A ures, a transmitting sing a 'single rod having unv,eqru -lcross sect1onal dimensions d rod ben19; rigidly clamped onee'nd and being prots freeen'dwithgnie isfor developotoelecti icsigna n d actuatingmeans for setting saidjrod ntofree' v bration, a receiving statio' ineansfor tr n1 treatment agsaisiio sear-acne ng station,

a single rod at the receivingstation of like "Q characteristics assaid first, rod rigidly supported atone end 'dprovidedat ts free end with means cooperating in thetranslat-mn oft said photoelectric signals into varying light corresponding with the transmitted picture, 190

actuating means for setting each of said rods into free vibration, and means for simultaneously operating said actuating means.

8. In a system for the electrical transmission of pictures, a transmitting station com- '105 prising a rod clamped at one end and provided with a photoelectric cell at its free end, actuating means for setting said rod into free vibration. a receiving station, means for transmitting from said photoelectric cell to 'iilo said receiving station electrical signals varying in accordance with the intensity of light from the picture to be transmitted, means at the receiving station for translating said varying electrical signals into correspondinglv varyin, ,1- light, a rod rigidly mounted at one end and provided at its free end with a mirrow supported in the path of light from said translating means, said rod having the same 7 3 characteristics as the rod at the transmittlng -12 station, actuating means for setting into free vibration the rod at the receiving station, and means for simultaneously operating both of said actuating means.

9. A system in accordance with claim 1 wherein the rod has an oblong cross-section.

10. In a system for theelectrical transmission of pictures, a rod supported at one end and carrying an optical instrument at its free 1 end, said rod having two unequal cross-secpath 70 misled receiving rod na system fo rtlieelectri cal tran sini s'sion tional dimensions, and means for setting said rod into vibration byan impulse applied diagonally to one side thereof. 7

11. In a system for the electrical transmission of pictures, a rod rigidly supported at one end, said rod having two different periods of vibration in two different planes at an angle to one another, expressed by two large coprime numbers differing from each other by a small number, an optical instrument controlled by the movement of the free end of said rod, and energizingmeans for setting said rod into free vibration.

12. In a system for the electrical transmission ofpictures, a rod rigidly supported at one end, said rod having two different periods of vibration in two different planes at an angle to one another, expressed by two large co-prime numbers differing from each other by a small number, an optical instrument con- I trolled by the movement of the free end of I .i said rod, and means for momentarily flexing said ro'd diagonally.

13. A system in accordance with claim 11 wherein two similar rods are provided, the energizing means affects both, and one of said rods is furnished with means for slightly varying its period of vibration.

In witness whereof, the above specification is signed in the name of LUDWIK SILBERSTEIN,

by Y

CHARLES VV. MARKUS,

Ommm'ttee 0f the Person and Estate of Luella-27c Silberstein. 

